System and method for correcting stitch and roll error in a staggered full width array printhead assembly

Abstract

A method evaluates printhead position in a staggered full width array (SFWA) printhead assembly. The method includes selecting a first printhead configuration for printing a first test pattern on an image receiving member, generating positional correction data for roll and stitch displacements obtained from captured image data of the first test pattern, comparing the positional correction data to at least one threshold in a displacement range, and operating at least one printhead actuator in accordance with the positional correction data in response to the positional correction data exceeding at least one predetermined threshold in the displacement range.

What is claimed is: 
     
       1. A method for evaluating printhead position in an ink printing system comprising:
 selecting a first printhead configuration for printing a first test pattern; 
 generating with an imaging system image data of the printed first test pattern; 
 generating confidence level measurements by comparing the generated image data of the printed first test pattern with test pattern data stored in the ink printing system; 
 generating positional correction data for roll and stitch displacements obtained from the generated image data of the first test pattern in response to the generated confidence level measurements being less than at least one predetermined threshold; 
 comparing the positional correction data to at least one threshold in a displacement range; and 
 operating at least one printhead actuator in accordance with the positional correction data in response to the positional correction data exceeding the at least one predetermined threshold in the displacement range. 
 
     
     
       2. The method of  claim 1 , the first printhead configuration selection further comprising:
 selecting two printheads of at least four printheads in a staggered full width array (SFWA) printhead assembly. 
 
     
     
       3. The method of  claim 1 , the first printhead configuration selection further comprising:
 selecting three of at least four printheads in the SFWA printhead assembly. 
 
     
     
       4. The method of  claim 1 , the generation of confidence level measurements further comprising:
 generating a roll displacement confidence level measurement for portions of the first test pattern in the generated image data that are used to evaluate roll displacement; 
 comparing the roll displacement confidence level measurement to a predetermined threshold for roll displacement; and 
 generating the positional correction data for a roll displacement in response to the roll displacement confidence level measurement being less than the predetermined threshold for roll displacement. 
 
     
     
       5. The method of  claim 1 , the generation of confidence level measurements further comprising:
 generating a confidence level measurement for portions of the first test pattern in the generated image data that are used to evaluate stitch displacement; 
 comparing the confidence level measurement to a predetermined threshold for stitch displacement; and 
 generating the positional correction data for a stitch displacement in response to the confidence level measurement being less than the predetermined threshold for stitch displacement. 
 
     
     
       6. The method of  claim 4 , the generation of confidence level measurements further comprising:
 generating a stitch displacement confidence level measurement for portions of the first test pattern in the generated image data that are used to evaluate stitch displacement; 
 comparing the stitch displacement confidence level measurement to a predetermined threshold for stitch displacement; and 
 generating the positional correction data for a stitch displacement in response to the roll displacement confidence level measurement being less than the predetermined threshold for roll displacement and the stitch displacement confidence level measurement being less than the predetermined threshold for stitch displacement. 
 
     
     
       7. The method of  claim 6  further comprising:
 comparing the generated positional correction data for the roll displacement and the positional correction data for the stitch displacement to the at least one predetermined threshold in the displacement range; and 
 operating the at least one printhead actuator in accordance with the positional correction data for the roll and stitch displacements in response to the positional correction data for the roll and stitch displacements being within a predetermined range about the predetermined threshold in the displacement range. 
 
     
     
       8. The method of  claim 7  further comprising:
 computing positional correction data for a printhead in the printhead assembly not in the first printhead configuration; and 
 operating at least one other printhead actuator in accordance with the computed positional correction data for the printhead not in the first printhead configuration in response to the computed positional correction data being less than the at least one predetermined threshold in the displacement range by no more than a predetermined amount. 
 
     
     
       9. The method of  claim 7  further comprising:
 selecting a second printhead configuration that is different than the first printhead configuration; 
 generating a second test pattern image with the second printhead configuration in response to the positional correction data for the roll displacement and the positional correction data for the stitch displacement exceeding the at least one predetermined threshold in the displacement range by no more than a predetermined amount. 
 
     
     
       10. The method of  claim 9  further comprising:
 generating image data of the second test pattern; 
 generating positional correction data for roll and stitch displacements obtained from the generated image data of the second test pattern; 
 comparing the positional correction data generated with reference to the second test pattern to at least one threshold in a second displacement range; and 
 operating at least one printhead actuator in accordance with the positional correction data generated with reference to the second test pattern in response to the positional correction data generated with reference to the second test pattern exceeding at least one predetermined threshold in the second displacement range. 
 
     
     
       11. A system for evaluating printhead position in an ink printing system comprising:
 a plurality of printheads configured to eject ink to form a first test pattern; 
 an imaging system configured to generate image data of the printed first test pattern; 
 an image evaluator configured to generate confidence level measurements by comparing the generated image data of the printed first test pattern with test pattern data stored in the ink printing system and to generate positional correction data for roll and stitch displacements detected in the generated image data of the first test pattern in response to the generated confidence level measurements being less than at least one predetermined threshold; and 
 a controller coupled to the plurality of printheads, the image evaluator, and at least one printhead actuator coupled to the plurality of printheads, the controller being configured to operate the at least one printhead actuator in accordance with the positional correction data in response to the positional correction data exceeding at least one predetermined threshold in a displacement range. 
 
     
     
       12. The system of  claim 11 , the image evaluator being further configured to select a first printhead configuration that uses two printheads of at least four printheads in the plurality of printheads to form the first test pattern. 
     
     
       13. The system of  claim 11 , the image evaluator being further configured to select a first printhead configuration that uses three printheads of at least four printheads in the plurality of printheads to form the first test pattern. 
     
     
       14. The system of  claim 12 , the image evaluator being further configured to compare roll displacement confidence level measurements for portions of the first test pattern used to evaluate roll displacements to a predetermined threshold for roll displacements and to generate the positional correction data for a roll displacement in response to the confidence level measurements being less than the predetermined threshold for the roll displacements. 
     
     
       15. The system of  claim 12 , the image evaluator being further configured to compare confidence level measurements for portions of the first test pattern used to evaluate stitch displacements to a predetermined threshold for stitch displacements and to generate the positional correction data for a stitch displacement in response to the confidence level value being less than the predetermined threshold for stitch displacements. 
     
     
       16. The system of  claim 14 , the image evaluator being further configured to compare stitch displacement confidence level measurements for portions of the first test pattern used to evaluate stitch displacement to the predetermined threshold for stitch displacements and to generate the positional correction data for a stitch displacement in response to the roll displacement confidence level measurements being less than the predetermined threshold for roll displacements and the stitch displacement confidence level measurements being less than the predetermined threshold for stitch displacement. 
     
     
       17. The system of  claim 16 , the image evaluator being further configured to compare positional correction data generated for the roll displacement and positional correction data for the stitch displacement to the at least one predetermined threshold in the displacement range and to operate the at least one printhead actuator in accordance with the positional correction data generated for the roll and stitch displacements in response to the positional correction data generated for the roll and stitch displacements being within a predetermined range about the at least one predetermined threshold in the displacement range. 
     
     
       18. The system of  claim 17 , the image evaluator being further configured to compute positional correction data for a printhead not in the first printhead configuration and to operate at least one other printhead actuator in accordance with the computed positional correction data generated for the printhead not in the first printhead configuration in response to the computed positional correction data being less than the at least one predetermined threshold in the displacement range by no more than a predetermined amount. 
     
     
       19. The system of  claim 18 , the image evaluator being further configured to select a second printhead configuration that is different than the first printhead configuration, and to generate a second test pattern in response to the positional correction data generated for the roll and stitch displacements exceeding the at least one predetermined threshold in the displacement range by no more than a predetermined amount. 
     
     
       20. The system of  claim 19 , the image evaluator being further configured to generate positional correction data for roll and stitch displacements obtained from image data of the second test pattern generated by the imaging system, and to operate at least one other printhead actuator in accordance with the positional correction data generated with reference to the second test pattern in response to the positional correction data generated with reference to the second test pattern being within a predetermined range about the at least one predetermined threshold in the displacement range.